1. Field of the Invention
The present invention relates generally to consumer personal audio playback devices, and more specifically, to a personal audio playback device that alters the gain of playback program material in response to environmental sounds.
2. Background of the Invention
Consumer audio playback devices are in widespread use. Ever since the development of miniaturized cassette players, portable entertainment has permitted people to carry around their desired personal listening material. More recently, miniature players incorporating flash-memory, hard drives and optical storage media to store program material have been developed, and some players incorporate LCD screens that permit the viewing of video information along with the associated audio program.
In order to provide the best listening experience, the headphones used with present-day personal audio devices have improved to the point that outside environmental sounds are attenuated quite severely and the transducers themselves have improved to provide very high acoustic program levels from typically low power levels available from such devices.
Although the increased loudness and environmental attenuation is preferable for uninterrupted listening, the possibility of intrusion of desirable or sounds indicative of danger has also been reduced. For example, it has become increasingly difficult to get the attention of a personal audio device user in order to converse with them, and conversation between persons using personal audio devices tends to be mutually exclusive of such use. For instance, a person generally must turn off or extremely attenuate their program material in order to conduct a conversation, or must remove one or both headphone elements from their ears. As another example, a pedestrian listening to audio via such a device may not notice a vehicle horn or siren that is alerting them to a hazard.
One solution to the above-described problems is to use headphone elements that “leak” more environmental sound into the user's ear, thus permitting the possibility of the environmental sound overcoming the loudness of the program material. However, the use of more leaky headphone elements runs contrary to the desired purpose of providing an isolated listening experience. For example, a headphone element that will provide enough leakage to alert a pedestrian to a car horn would not be suitable for a person desiring to use the same headphones while an undesirable environmental noise is present, such as listening while operating a vacuum cleaner. Further, with the tendency to increase the volume of the program material to overcome undesirable noise, damage to hearing becomes an issue, as the human ear is sensitive to prolonged high volume levels, whether desirable program material or undesirable noise.
Recently, the technique of noise cancellation has been applied to consumer headphones. A microphone detects ambient sounds and a circuit modifies the program audio electrical signals to attempt to subtract the ambient sounds, thus improving the user's listening experience and making it less likely that a user will increase the volume of the program material to overcome ambient sounds. However, such a device does not solve the above-described problems of providing for conversations, and if an environmental noise indicative of a hazard is not sufficiently loud to as to defeat the noise-canceling mechanism, then the noise cancellation will also not produce a desirable result.
Therefore, it would be desirable to provide a personal consumer audio device that provides a quality individual program listening experience in the presence of environmental noise, while providing for communications with others and awareness of environmental sounds indicative of a hazard.